Novikov S.,Aalto University |
Lebedeva N.,Aalto University |
Journal of Sensors | Year: 2015
We report about technology of fabrication and optimization of a gas sensor based on epitaxial graphene. Optimized graphene/metal contact configuration exhibited low contact resistance. Complementary annealing of graphene sensor after each gas exposure led to significant improvement in the sensing performance. The response of the annealed sensor to the nitrogen dioxide (NO2) was tenfold higher than that of an as-fabricated graphene sensor. NO2 concentration as low as 0.2 parts per billion (ppb) was easily detectable. Devices have high signal-to-noise ratio. The detection limit of the graphene sensor was estimated to be 0.6 ppt (parts per trillion). The present technology with additional annealing improves the performance of the graphene based sensor and makes it suitable for the environmental nitrogen dioxide gas monitoring. © 2015 S. Novikov et al.
Kalmbach C.-C.,Physikalisch - Technische Bundesanstalt |
Schurr J.,Physikalisch - Technische Bundesanstalt |
Ahlers F.J.,Physikalisch - Technische Bundesanstalt |
Muller A.,Physikalisch - Technische Bundesanstalt |
And 3 more authors.
Applied Physics Letters | Year: 2014
Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 107. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8â€‰×â€‰10-8/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance. © 2014 AIP Publishing LLC.
Semenov Yu.,VNIIM |
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2010
Series resonance (SR) method was investigated for the realization of 100 mH inductance at 1 kHz in VNIIM and MIKES. Practical details of the application of this method and comparison with the results of realization by the Maxwell-Wien Bridge method are presented. Results showed that 1 σ uncertainty of the 100 mH realization by SR method at 1 kHz can be at the level of parts in 10 6. © 2010 IEEE.
Palafox L.,Physikalisch - Technische Bundesanstalt |
Behr R.,Physikalisch - Technische Bundesanstalt |
Nissila J.,MIKES |
Schurr J.,Physikalisch - Technische Bundesanstalt
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2012
Josephson impedance bridges have been reported to provide uncertainties close to that from the best conventional bridges when comparing two 10-kΩ resistors. The accuracy of a few parts in 10 8 has been extended to the comparison of two 100-pF capacitance standards, significantly improving the uncertainty for these measurements at power line frequencies. Preliminary measurements of Josephson quadrature bridges are also presented with uncertainties at the level of 1.6 × 10 -6 (k = 1). © 2012 IEEE.
Merev A.,TUBITAK - Marmara Research Center |
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2014
The high-voltage DC measuring system based on bandgap voltage references has been used for high accuracy with low dynamic resistance up to 20 kV. The measuring system is stable output over a wide range of operating current and ambient temperature, and it is insensitive to effects due to leakage currents. One of the most important parameters of a reference system is its long-term stability. This paper describes the long-term performance of a high-voltage DC reference measuring system based on bandgap voltage references. © 2014 IEEE.